Method of vibrating core in concrete pipe making machine

ABSTRACT

The invention comprises a novel method of vibrating a core in a concrete pipe making machine. In a preferred embodiment, a novel core is inserted and vibrated simultaneously with formation of the cementitious pipe. Vibration may continue for a short period after pipe formation in order to insure complete compaction of material and elimination of voids.

April 11, 1972 F. A. TRAUTNER METHOD OF VIBRATING CORE IN CONCRETE PIPE MAKING MACHINE 3 Sheet-Sheet 1 Original Filed May 27, 1967 m T N E V m BY M JM v D W ATTORNEYIS April 11, 1972 F. A. TRAUTNER 3,655,842

METHOD OF VIBRATING CORE IN CONCRETE PIPE MAKING MACHINE Original Filed May 27, 1967 3 Sheet-Sheet 2 INVENIOR firdzimrzdd.fiuuizer Bl f Y \iwlfic V ATTORNEYS April 11, 1972 F. A. TRAUTNER 3,655,842

METHOD OF VIBRATING CORE IN CONCRETE PIPE MAKING MACHINE Original Filed May 27, 1967 3 Sheet-Sheet 5 INVENTOR j z'dzmdd. 5mm

0 ATTORNEY5 United States Patent 3,655,842 METHOD OF VIBRATING CORE IN CONCRETE PIPE MAKING MACHINE Ferdinand A. Trautner, Newton Upper Falls, Mass., assignor to Viropac, Inc., Sioux City, Iowa Original application May 27, 1967, Ser. No. 638,010. Divided and this application Oct. 17, 1969, Ser. No.

Int. Cl. B28b 1/46, 7/00, 21/00 US. Cl. 264-72 9 Claims ABSTRACT OF THE DISCLOSURE CROSS REFERENCE TO RELATED APPLICATION This is a divisional application of Ser. No. 638,010, filed May 27, 1967, now abandoned.

BACKGROUND OF THE INVENTION The invention relates generally to the formation of concrete pipe, and particularly presents a solution to the problem of residual strain created by the troweling of zero slump concrete with rotary motion. In the usual pipe forming apparatus, the outer form of the pipe is stationary. Thus, rotary motion by the packerhead imparts a stress to the concrete mix, such stress being particularly disturbing in the event the concrete pipe is supplied with reinforcing wire. It has been found that such wire may be strained beyond its yield point causing permanent bending as well as deflection of the wire, making the completed pipe product unsatisfactory. Furthermore, because of the difference in modulus of elasticity between steel and concrete relieving such undesirably induced stress after the pipe is formed causes unnecessary voids to be formed in the concrete pipe. Obviously, such voids reduce the strength of cured pipe and allow leakage in the pipe through the voids.

In the case of non-reinforced pipe residual stress movement of the concrete causes cracks to form in the pipe thereby reducing strength of the pipe and permitting leaks. As a result of these encountered problems, many purchasers of concrete pipe refuse to accept pipe formed by a rotating packerhead or rollerhead method.

The prior art is not entirely devoid of vibrating cores used in the manufacture of concrete pipe. For example, the US. patent to E. Robbins, No. 1,504,834, illustrates a core for a pipe form inserted into and withdrawn from the form therebeneath by means of controlled fluid pressure. US. Pat. No. 1,961,981 to Pechstadt also discloses a movable core for a pipe form, and a tamper for compacting the cementitious material. A further improvement to the basic concept of these two patents is disclosed by US. Pat. No. 2,544,453 to Gaudin which illustrates a vertically movable vibrating core insertable into and withdrawable from a pipe form.

However, none of these patents nor any material presently available in the art of forming concrete pipe discloses a solution to the residual stress problem discussed above 3,655,842 Patented Apr. 11, 1972 ice which is encountered in the current practice of the manufacture of pipe which employs the use of a vertically disposed form and a packerhead which moves slowly along the axis of the form while rotating and while concrete is poured in to form the pipe.

The instant invention overcomes the disadvantages of the prior art by permitting the formation of concrete pipe by the rotating packerhead method without inducing residual stress either in the concrete or in the reinforcing wire, if used. By employing a vibrating core together with a rotating packerhead as the concrete pipe is formed, residual stresses are avoided due to vibratory motion being imparted to the concrete and reinforcing wire during the pipe forming operation. Of further significance is the fact that the vibrating core of this invention may be used on concrete pipe formed by a variety of other methods such as by spinning, vibration, or tamping, before the pipe is cured so as to relieve all residual stress, fill voids, compact and density the concrete and induce a more intimate bond between reinforcing wire and the concrete mix prior to curing of the pipe. Finally, desirably larger aggregate may be used in the concrete mix for concrete pipes resulting in a decrease in absorption of the pipe wall because vibration by the core will cause thorough mixing of the concrete as well as a better coating of sand and aggregate particles with cement.

SUMMARY The object of the invention is to provide a concrete pipe making method which completely negates residual strain caused by the standard pipe forming apparatus by employing a vertically movable internal vibrating core to the pipe as it is formed. In the primary embodiment, the vibrating core is adapted for use with a rotating packerhead as the concrete pipe is formed. A series of vibrators are attached internally of the core, preferably, and are activated sequentially as the core enters the pipe form. Once the pipe is formed, the core is lowered and raised again through the green pipe, and is vibrated to assure elimination of residual voids and stresses. Then the core is lowered only a short distance from the top, or spigot end of the green pipe, and raised, while vibrating, three more times to even further assure complete compaction of the green pipe. Settling near the spigot end will occur, so a small amount of cementitious material is added to complete the spigot end of the pipe. After the third terminal pass, the core is lowered and the completed pipe removed for curing.

BRIEF DESCRIPTION OF THE DRAWINGS Details of construction and operation according to the preferred embodiments of the invention will become readily apparent by reference to the following drawings wherein:

FIGS. 1 through 5 are front elevational views showing the invention as applied to a concrete pipe making machine of the type commonly used in the industry; these figures show the sequence of operations in forming concrete pipe; 1

FIGS. 6 through 9 are similar to FIGS. 1 through 5 and show the sequence of operations in forming a concrete pipe according to this invention in another embodiment; and

FIG. 10 is a sectional view of the means interengaging the vibrating core and the rotating packerhead and applies to both embodiments of the invention as shown by FIGS. 1 through 5 and by FIGS. 6 through 9.

3 DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings by reference character and in particular to FIGS. 1 through 5 thereof, the invention is shown in combination with a modified pipe making machine of the type commonly used in the industry today. The pipe making machine comprises a pipe form of generally cylindrical configuration, which may have circular corrugations therein. Form 10 includes an upper, spigot end 12 and a lower, diverging frusto-conical skirt forming a bell end 14. A platform 16 is provided for form 10, and includes a circular opening 18 centrally located beneath bell end 14. Platform 16 may be a turntable for indexing of work.

Interiorally of hell end 14 is a pallet 20 having a circular opening 22 therein, generally concentrically spotted with respect to opening 18 in platform 16. Pallet 20 is slightly movable vertically within bell end 14 for initial formation of the bell end of the pipe.

A frame superstructure generally indicated by 24 is located above platform 16 and includes a cementitious material boot or hopper 26 and a conveyor 28 for filling form 10. Numeral 30 indicates a packerhead, rollerhead, or circular, powered trowel, each of which is known in the art, which distributes and compacts material against the form from bell end 14 upwardly to form the pipe, travelling through mix provided from boot 26 and conveyor 28. Frame 24 supports a vertically movable crosshead (not shown) which drives shaft 34 and distributor 30.

A pit designated at 36 contains the major portion of the instant invention. For ease of explanation, parts will be described from the base of pit 36, upwardly to turntable or platform 16. Mounted in the base of pit 36 is a caisson or hydraulic cylinder 33 having an internal vertically travelling piston (not shown) operatively connected to a piston rod 40 (FIG. 2). A frame assembly comprising a plurality of radially spaced vertical standards 42, 42 is arranged concentrically about cylinder 38 and beneath opening 18 in platform 16. A circular base block plate 44 is secured about cylinder 38 at the floor of pit 36 to standards 42, 42. A similar upper block plate 46 is mounted near the upper ends of standards 42, 42. Between plates 44 and 46 are located a series of radially spaced guide rods 48, 48. Plates 44 and 46 serve additionally as the lower and upper limits respectively of the travel of a bearing block assembly 50, having bearing sleeves formed therein (not shown) about guide rods 48, 48, for free movement therealong. Block assembly 50 cooperating with guides 48, 48 also serves to prevent axial rotation of the vibrating core of the invention.

A cylindrical support casing 52 is mounted on top of block assembly 50 and is aflixed to the free end of piston rod 40. A circular opening 54 is provided in the lower face of casing 52 to entry of cylinder 38 when the invention is in a static, initial stage as shown in FIG. 1. A thrust rod 56 is fixed to piston rod '40 through the upper portion of casing 52 having core platform support 58 mounted thereon. Thus axial stability and limitation of travel of core 60 are imparted substantially beneath the lower terminal end of core 60 so that complete insertion into form 10 is allowed, without interfering with the other operating parts of the apparatus, as shown in FIG. 4. Vibrating core 60 is mounted directly on platform 58 being provided with a series of internally spaced vibrators 62 (FIG. 3).

Immediately beneath platform 16 is a pallet lift assembly 64 (FIG. 2) for forming the bell end of the pipe in the initial stage of operation. Such an assembly is described in detail in US. Patent No. 3,083,433 to M. Tiller. For purposes of the instant invention, assembly 64 (FIG. 2) includes a vibrating plate 66 having legs 68 thereon for contacting, lifting and vibrating pallet 20. A drive plate 70 is secured to and immediately beneath vibrating plate 66, plates 66 and 70 being rotatably mounted in frame 42. A motor with suitable gearing drives plate 70 to rotate pallet 20 during the bell forming stage of the pipe making operation. Assembly 64 is raised and lowered by suitable lift means (not shown) and is limited in travel by a pair of limit stops 72, 74.

A second embodiment of the invention is shown in FIGS. 6 through 9 wherein the pipe is formed without aid of pallet lift assembly 64. As in the embodiment illustrated in FIGS. 1 through 5, the pipe making machine includes a bell-down form 10, super-structure 24, packerhead 30 with drive shaft 34 a, material hopper 26 and platform or turntable 16. In pit 36 is a caisson or hydraulic cylinder 38 having a piston rod 40 actuated by fluid pressure. Core platform 58 is mounted directly on piston rod 40 (FIG. 8). Controlled movement for platform 58 is provided by a plurality of radially spaced rods 76, 76 mounted directly in the floor of pit 36 and secured at their upper ends to frame portions 78 beneath platform 16. Vibrators 80, 80 are attached to bell end 14 of form 10 to compact material in the bell of the pipe, formed between pallet 20 and form 10. Finally, rollers 82, 82 are mounted beneath platform 16 to frame 78 to guide core 60 into and out of form 10.

FIG. 10 illustrates the specific connection between rotating packerhead 30 and non-rotating core 60. Packerhead 30 includes an internal rotating drive shaft 84 which is threaded at its terminal end 86 to receive a bearing and pilot stud housing 88. Non-rotating support shaft 90 is mounted internally of rotating housing 88 by means of a twin series of inclined roller thrust bearings 92, 92 which are adapted to receive both axial and radial stress on the order of 20,000 pounds and 10,000 pounds respectively. A pilot stud 94 is formed on the lower end of support shaft 90 and is tapered at its thrust end so as to guide itself into lock housing 96 of non-rotating core 60 without aid of external guide means. Pilot stud 94 is formed with a lock recess 98 which cooperates with radially spaced locking studs 100, each actuated by hydraulic pressure through lines 102 against piston 104. Studs 100 and recess 98 are formed with cambered abutting faces so that upon relief of pressure in lines 102, pilot stud 94 will separate from core lock housing 96 by axial movement above, forcing lock studs 100 into their receiving chambers 106.

The operation of the two embodiments of the invention are similar. In the embodiment shown in FIGS. 1 through 5, the invention is depicted first, in FIG. 1, in a static position prior to the pipe making operation. In this position, platform or turntable 16 may be moved (now shown) to place form 10 into position, centrally beneath packerhead 30 and above core 60.

The pipe forming operation begins by the lowering of packerhead 30 together with housing 88 and pilot stud 94 into form 10 and the raising of core 60 by fluid pressure in cylinder 38. Hydraulic pressure is introduced through lines 102 to force studs 100 into recess 98 so that rotating packerhead or rollerhead 30 and core 60 are firmly engaged. Mix is then poured into form 10 from conveyor 28, and pallet lift assembly 64 is raised to the position shown in FIG. 2. The bell end of the pipe is then formed in the manner disclosed in US. Patent 3,083,433,

' as discussed above, by rotating and vibrating the pallet assembly 64. Rotation of packerhead 30 is initiated, in a direction opposite the rotation of pallet 20.

When the bell end portion of the pipe has been completed, assembly 64 is lowered to the static position shown in FIG. 3. Packerhead 30 is then raised through the mix, together with core 60 which is forced upwardly by fluid pressure in cylinder 38 acting through piston rod 40, thrust rod 56, and core platform 58. As each vibrator 62 passes bell-end 14 of form 10, it is activated by a trip switch or other suitable energizing means (not shown) to vibrate that portion of the core. When packerhead 30 has reached the top or spigot end 12 of form 10, rotation ceases, fluid pressure in line 102 is relieved, and packerhead 30 is lifted from core 60, as illustrated in FIG. 4. Vibration of core 60 by vibrators 62 is continued for a short time to complete compaction of mix, particularly around spigot end 12 of form 10, and to assure the complete elimination of any residual stress in the completed pipe which may have been caused by the rotation of packerhead 30.

Once vibration is satisfactorily completed core 60 is withdrawn from the finished pipe by cylinder 38, turntable 16 is moved to place a new form into position and to remove the newly completed green pipe.

Of course, vibrators 62 might be replaced by or supplemented with vibrators located externally of the invenion, as on form 10 (not shown). The important point is that vibratory motion be imparted to the mix as the pipe is being formed to assure complete compaction of the mix.

The general methodology outlined above may be supplemented by additional steps if desired. These steps will assure an even more satisfactory product. Once packerhead 30 has reached the top or spigot end 12 of form 10, packerhead 30 together with core 60 may be lowered back to the initial position. A second pass, or vertical movement of core 60 through the newly formed green pipe is made, with the vibrators energized, in order to even further densify smooth and compact the concrete pipe. Once the second pass is complete, and core 60 has reached its uppermost vertical status, the vibrators are left activated with the core 60 remaining in a static position for a period of from one to three minutes depending upon the slump rating of the concrete. The drier the mix, the longer this period of vibration should be. Then core 60 and packerhead 30 should be lowered once more, but only a short distance, such as from one and one-half to two feet, and raised again to the upper most vertical status in order to further settle and compact spigot end 12 of the pipe being formed. This short or terminal pass should be repeated three times, with the vibrators 62 activated, adding a little mix at end 12 of the form as the newly formed pipe settles due to the vibration. At the moment of completion of the third termina pass, all vibraors should be deactivated immediately to terminate settling. Then packerhead 30 is released from core 60 and core 60 is withdrawn from the pipe as outlined previously.

Of course, packerhead 30 and core 60 may be raised either by cylinder 38, thrust rod 56 and piston rod 40, or they may be lifted from above by the vertically movable crosshead (not shown) which drives the shaft 34 and distributor 30.

The operation of the second embodiment of the invention shown in FIGS. 6 through 9 is similar, except that bell end 14 of the pipe is formed by vibration induced by vibrators 80 located therearound. Once the bell end is formed, vibrators 80 are turned off, and the remainder of the operation discussed above is completed.

Green pipe formed from cementitious material by a rotary trowel method or other methods common in the art may be transferred to the invention while still in its mold to be vibrated by inserion of core 60 thereinto. This operation will remove residual stress in the gree pipe and give the cured pipe the structural integrity assured by use of the present invention during the initial forming stage of the pipe.

Three-edge bearing tests were made on concrete pipe formed by the invention and results were compared with results obtained from testing pipe manufactured without the aid of the instant invention. Five test specimens were manufactured having only 74% of the steel reinforcement used in our specimens manufactured by the older process. These tests were conducted to specifications for three-edge bearing tests contained in Tentative Specifications for Reinforced Concrete Culvert, American Society for Testing and Materials in 1963. The values listed in the D-load columns below are test loads expressed in pounds per linear foot per foot of pipe diameter. The four specimens manufactured by the older process were made according to the ASTM requirements for Class IV reinforced concrete pipe. The test results of the pipe manufactured according to the invention were as follows:

Each pipe was eight feet long, two feet in diameter and had a wall thickness of three inches, and was given ten hours of moist curing.

The four specimens manufactured in the manner known in the art yielded the following test results:

D-load D-load 0.01 ultimate, Tested crack, lbs. lbs.

Made:

x x+50 days 2, 400 3, 280 x x+20 days. 2,020 3,100 1, 970 3, 320 2,100 3, 470

These latter specimens compare precisely in size to the former, save that these four specimens contained a significantly greater amount of reinforcing steel, and were aged for a considerably longer period of time. Yet the pipes formed according to the present invention performed as well as those made in a usual manner.

I claim:

1. A method of relieving residual torroidal strain in green cementitious pipe being formed by rotary trowel action exerting radial outward pressure comprising: I

(a) inserting of a core having an external diameter approximating the internal diameter of said green pipe, and a length corresponding to that of said pipe; and

(b) vibrating said core during insertion into said green pipe whereby the material of said pipe is settled and voids formed therein during manufacture are filled.

2. The method as recited in claim 1 wherein insertion and vibration of said core are made to occur simultaneously with the formation of said cementitious pipe.

3. The method as recited in claim 1 wherein vibration of said core is made to occur simultaneously with the formation of said cementitious pipe, and to continue after completion of pipe formation, while said core remains inserted completely in said formed pipe.

4. The method as recited in claim 1 wherein the step of vibrating the core during insertion into the green pipe comprises the further steps of:

(a) inserting and vibrating the core simultaneously with the formation of said cementitious pipe; and

(b) withdrawing the core and reinserting and vibrating the core again once the green pipe is formed.

5. The method as recited in claim 4 wherein the step of withdrawing the core and reinserting and vibrating the core once the green pipe is formed comprises the further steps of:

(a) continuing vibration of the core once reinsertion of the core is completed until further densification and compaction of the green pipe is completed;

(b) terminating vibration of the core; and

(c) removing the core from the green pipe.

6. The method as recited in claim 5 wherein the step of continuing vibration once reinsertion of the core is completed comprises the further steps of:

(a) partilaly withdrawing the core again as it continues to vibrate, a distance less than the length of said green pipe, and

(b) fully reinserting the core into the green pipe as vibration of the core continues.

7. The method as recited in claim 6 wherein the steps of partial withdrawal and full reinsertion of the vibrating core into the green pipe are repeated at least once.

8. The method as recited in claim 6 wherein the steps of partial withdrawal and full reinsertion of the vibrating core into the green pipe are conducted three times.

9. The method according to claim 1 wherein the pipe being formed is provided with wire reinforcement.

References Cited UNITED STATES PATENTS 1,770,154 7/1930 Day 264-69 8 2,356,852 8/ 1944 Hutchinson 26472 2,524,676 10/ 1950 Nielsen 25-41 J 2,544,453 3/1951 Gaudin 2536 5 FOREIGN PATENTS 591,792 4/ 1959 Italy 2536 ROBERT F. WHITE, Primary Examiner 10 J. R. THURLOW, Assistant Examiner US. Cl. X.R.

, UNf rED sums m'mwr OFFICE v CERTKFICATE 01 commTm- Patent No. 3,555,842 Dated April 11, 1972 F. A. 'Ir'autner Invcntofls) I It is certified that: error appears in the above-identificd pzitcnt' and that said Letters Patent: are hereby corrected as shown below:

Column 5, lin 41, change "termina" to --temina l- 1ine 6Q; dhange "g z e e'" to --gree n--.

, line 71 insert quotation marks before f'Ten'ta-tive lirge 72) after "Culvert, insert.-.-Storm Drain and Swer Pipe? (6-76-63'1) published by the-7 column 6, line 72 '(claim 6 char ag" "partilaly" to 'pai'tiily- Signed'and se ale d this 26th dayof June 1973.

(SEAL). 'Attest;

EDWARD .M.FLET( IHER,J R. V v I ROBERT GOTTSCHAL K Attestlng Qfflcer I Commissionot of Patents 

